Many students and professionals have no real understanding of what they are. They have learnt that “active power is good” and “reactive power is bad”, but few could actually explain what is reactive power, and what happens in an AC system.

And yet, in an AC system, the following types of ‘powers’ can be found:

instantaneous

active

reactive

distorting

apparent

The following document explains what they are, and why we want one type and not the other, what they imply in real systems. They also inlude the mathematical demonstrations of it.